Electrical impulses originating in the tissues of the heart cause the heart to cyclically contract. When, due to heart disease or tissue damage, the heart tissue fails to properly create and/or propagate these electrical impulses, an artificial electronic pace maker may be implanted to provide the necessary simulation.
Clinicians must be made aware of patients that have been treated with an implantable pacemaker due to the adverse effects that may result from the provision of certain drugs and/or medical procedures unknowingly upon a patient who has an implanted pacemaker. However, the clinician is not always made aware of the existence of an implanted pace maker within the patient, nor are pacemaker electrical pulses readily discernable when viewing a patient's electrocardiograph (ECG). Therefore, certain medical standards require that ECG monitoring and analysis systems include electronic pace maker pulse identification algorithms and labeling.
The detection of pacing stimulus artifacts from implanted electronic pace makers is sometimes difficult due the present use of sophisticated pacemaker pulse generation algorithms and low-energy output waveforms for stimulating the heart muscle. In addition, improvements in ECG collection and processing technology have reduced the noise artifacts that exist in the collected ECG signal. While this has improved ECG signal quality, it has made it harder to detect artificially generated stimulation.
The detection of electronic pacemaker pulse artifacts in an ECG signal is further complicated by the signal characteristics of the pacemaker pulses and the ECG signals themselves. The bandwidth of a normal ECG signal is generally between 0.5 and 150 Hz, with advanced applications of the ECG reaching a maximum of 300 HZ. On the other hand, the bandwidth of the pacemaker pulse signals is generally between 250 Hz and 10 kHz. Therefore, there is very little noise generated by artificial stimulation of the heart that corrupts the ECG signal outside of 60 Hz line frequency noise.
Although it is relatively easy to isolate and enhance the physiological signal for the purposes of ECG analysis, it is more complicated to acquire both the physiological signal and the pacemaker pulse signals for the optimum assessment of each. This is because the large bandwidth of the pace maker pulse signals (250 Hz to 10 KHz) overlaps with the frequency content of other noise generated by man-made electrical sources or static. These other noise sources can be very large and intermittent. As a result, they can corrupt or saturate the digital acquisition of the low-frequency physiological signal. Furthermore, the signal-to-noise characteristics of the acquisition hardware required for the physiological signal is much higher than the signal-to-noise characteristics for the pacemaker signals. As a result, a dual path for each type of signal is warranted.